The present invention relates generally to welding, and, more specifically, to rim welding a thin disk to a tubular body.
A new pressure sensor is being developed which includes a tubular body having a central bore extending therethrough which includes internal threads. The body also includes a shallow counterbore defining a disk seat in which a very thin metal disk is disposed. It is required to weld the disk to the body around its circumference for providing a fixed and sealed joint therebetween. The disk is about 10 mils in thickness for example, and will support one or more strain gauges at the center of its outer surface for measuring strain therein due to pressure acting against the inner face of the disk. Pressure will deflect the disk and in turn create strain in the gauges which may be used for an indication of the pressure being measured.
In preliminary attempts to weld the disk using a conventional pulsed Nd:YAG laser, the disk warped at the beginning of the weld cycle displacing the disk from its machined fit in the disk seat. As the weld process continues, the disk either moves away from its seat or is welded in the wrong location, or burns completely away leaving a large void at the rim. Initially tack welding the disk at various circumferential locations, and then completing the weld leads to residual stress distortions in the disk which are unacceptable in creating an effective pressure sensor using strain gauges on the outer surface of the disk.
Accordingly, it is desired to provide a suitable fixture for supporting the sensor body and disk for allowing welding of the disk rim to the body in its proper position and without undesirable residual distortion and stress in the welded disk.